Here are a few English phrases/idioms/expressions that seem to be similar to your idiom description and can be used as in your example. However, their general use doesn't seem to be as common. Also note that you have two different ideas contained within your idiom description. One idea is the "directing" or "telling/dictating" = controlling an intended audience, while the other is "casting a role" = projecting a role onto another (object). This is somewhat difficult and confusing if you are looking for a single English phrase. Using your sentence for examples (I changed the ending slightly), possibly one might fit best for you.
- "to run the show"
https://idioms.thefreedictionary.com/run+the+show
ex. “Their definition of God [those who claim that an All-Forgiving
God would never do this and that, etc.] is without basis; rather, they
are running the show with both the nature of God and the peoples' beliefs.”
- "to stage-manage"
https://www.thefreedictionary.com/stage-manage
ex. “Their definition of God [those who claim that an All-Forgiving
God would never do this and that, etc.] is without basis; rather, they
are stage-managing God to influence the peoples' beliefs.”
- "to project onto"
https://idioms.thefreedictionary.com/project+onto
ex. “Their definition of God [those who claim that an All-Forgiving
God would never do this and that, etc.] is without basis; rather, they
are projecting (their ideas) onto God to influence the peoples' beliefs.”